[ovs-dev] Is there a way to have a flow perform tbl_lookup twice?
YIMIN CHEN
ymchen.nbzj at gmail.com
Tue May 8 01:39:20 UTC 2012
Thank you!
Yimin
On Tue, May 8, 2012 at 9:29 AM, Jesse Gross <jesse at nicira.com> wrote:
> datapath/vport-gre.c
>
> On Mon, May 7, 2012 at 6:21 PM, YIMIN CHEN <ymchen.nbzj at gmail.com> wrote:
>> Hi Ben,
>>
>> Thank you for your reply! I am newbie to openflow development, please
>> pardon me if my problem description is not precise :)
>>
>> Could you please point me to the gre tunnel processing file, I would
>> like to take a look to understand it better.
>>
>>
>> Thanks!
>> Yimin
>>
>> On Tue, May 8, 2012 at 12:16 AM, Ben Pfaff <blp at nicira.com> wrote:
>>> With the normal way that gre tunnel processing works, you only get a
>>> shot at it after decap.
>>>
>>> Or maybe you're just describing the way that GRE tunnel processing
>>> works and don't need resubmit at all. It's hard to tell, since you
>>> keep changing your description and your requirements.
>>>
>>> On Mon, May 07, 2012 at 08:55:36AM +0800, YIMIN CHEN wrote:
>>>> I didn't quite yet understand why resubmit does not work for my case.
>>>> It could be the same flow table, I just need to search it twice:
>>>> -- once before decap, when hit, knows the flow needs to be decap'ed
>>>> and resubmitted to the table again
>>>> -- once after decap, with the destination IP of decap'ed packet.
>>>>
>>>> This does not work?
>>>>
>>>>
>>>> Thanks!
>>>>
>>>> On Sat, May 5, 2012 at 3:40 AM, Ben Pfaff <blp at nicira.com> wrote:
>>>> > The difference is that Yimin Chen wants to process the packet through
>>>> > two flow tables, one before and one after decap. With the normal way
>>>> > that gre tunnel processing works, you only get a shot at it after
>>>> > decap.
>>>> >
>>>> > On Fri, May 04, 2012 at 12:35:00PM -0700, Karl Yang wrote:
>>>> >> what is the difference between your this case and the "gre" tunnel
>>>> >> processing case within data path code?
>>>> >>
>>>> >> On Fri, May 4, 2012 at 10:05 AM, Ben Pfaff <blp at nicira.com> wrote:
>>>> >>
>>>> >> > No.
>>>> >> >
>>>> >> > On Fri, May 04, 2012 at 10:16:14AM +0800, YIMIN CHEN wrote:
>>>> >> > > Hi Ben,
>>>> >> > >
>>>> >> > > My goal is to implement a decap action that would decap a packet with
>>>> >> > > external IP addresses, and then have the decapped packet, with
>>>> >> > > internal IP addresses, do a flow lookup again.
>>>> >> > >
>>>> >> > > Can this be achieved using resubmit?
>>>> >> > >
>>>> >> > > Thanks!
>>>> >> > > Yimin
>>>> >> > >
>>>> >> > > On Fri, May 4, 2012 at 9:37 AM, Ben Pfaff <blp at nicira.com> wrote:
>>>> >> > > > You can read PORTING in the root of the tree.
>>>> >> > > >
>>>> >> > > > It would be best if you'd explain your goal first, instead of doing a
>>>> >> > > > deep dive into implementation details.
>>>> >> > > >
>>>> >> > > > On Fri, May 04, 2012 at 09:20:38AM +0800, YIMIN CHEN wrote:
>>>> >> > > >> Hi Ben,
>>>> >> > > >>
>>>> >> > > >> Thank you for the detailed information! I read this part of the code,
>>>> >> > > >> and have some confusion. Can you please review the following to see if
>>>> >> > > >> my understanding of code is correct?
>>>> >> > > >>
>>>> >> > > >> 1) ofproto/ code is userspace code, and datapath/ code is the actual
>>>> >> > dp code.
>>>> >> > > >> 2) ofproto handles the rule insertion from control plane, and datapath
>>>> >> > > >> handles the actual flow lookup.
>>>> >> > > >> 3) resubmit is handled in userspace? I saw the resubmit logic
>>>> >> > > >> xlate_nicira_action() is in ofproto I didn't see find any code in
>>>> >> > > >> datapath that handles resubmit, not even in ovs-ofctl.c. Is
>>>> >> > > >> xlate_nicira_action() doing flow insertion with resubmit action or
>>>> >> > > >> actually performing the dp actions? I am confused.
>>>> >> > > >>
>>>> >> > > >> What is the relationship between ofproto userspace and the dp code?
>>>> >> > > >> what is the difference between xlate table action and odp action?
>>>> >> > > >>
>>>> >> > > >> I think I am very confused, if there is any documentation I can read
>>>> >> > > >> to understand this design better, would you please give me a pointer?
>>>> >> > > >>
>>>> >> > > >> Thanks!
>>>> >> > > >> Yimin
>>>> >> > > >>
>>>> >> > > >> On Thu, May 3, 2012 at 11:30 AM, Ben Pfaff <blp at nicira.com> wrote:
>>>> >> > > >> > It's documented in nicira-ext.h:
>>>> >> > > >> >
>>>> >> > > >> > /* Action structures for NXAST_RESUBMIT and NXAST_RESUBMIT_TABLE.
>>>> >> > > >> > *
>>>> >> > > >> > * These actions search one of the switch's flow tables:
>>>> >> > > >> > *
>>>> >> > > >> > * - For NXAST_RESUBMIT_TABLE only, if the 'table' member is not
>>>> >> > 255, then
>>>> >> > > >> > * it specifies the table to search.
>>>> >> > > >> > *
>>>> >> > > >> > * - Otherwise (for NXAST_RESUBMIT_TABLE with a 'table' of 255,
>>>> >> > or for
>>>> >> > > >> > * NXAST_RESUBMIT regardless of 'table'), it searches the
>>>> >> > current flow
>>>> >> > > >> > * table, that is, the OpenFlow flow table that contains the
>>>> >> > flow from
>>>> >> > > >> > * which this action was obtained. If this action did not
>>>> >> > come from a
>>>> >> > > >> > * flow table (e.g. it came from an OFPT_PACKET_OUT message),
>>>> >> > then table 0
>>>> >> > > >> > * is the current table.
>>>> >> > > >> > *
>>>> >> > > >> > * The flow table lookup uses a flow that may be slightly modified
>>>> >> > from the
>>>> >> > > >> > * original lookup:
>>>> >> > > >> > *
>>>> >> > > >> > * - For NXAST_RESUBMIT, the 'in_port' member of struct
>>>> >> > nx_action_resubmit
>>>> >> > > >> > * is used as the flow's in_port.
>>>> >> > > >> > *
>>>> >> > > >> > * - For NXAST_RESUBMIT_TABLE, if the 'in_port' member is not
>>>> >> > OFPP_IN_PORT,
>>>> >> > > >> > * then its value is used as the flow's in_port. Otherwise,
>>>> >> > the original
>>>> >> > > >> > * in_port is used.
>>>> >> > > >> > *
>>>> >> > > >> > * - If actions that modify the flow (e.g. OFPAT_SET_VLAN_VID)
>>>> >> > precede the
>>>> >> > > >> > * resubmit action, then the flow is updated with the new
>>>> >> > values.
>>>> >> > > >> > *
>>>> >> > > >> > * Following the lookup, the original in_port is restored.
>>>> >> > > >> > *
>>>> >> > > >> > * If the modified flow matched in the flow table, then the
>>>> >> > corresponding
>>>> >> > > >> > * actions are executed. Afterward, actions following the resubmit
>>>> >> > in the
>>>> >> > > >> > * original set of actions, if any, are executed; any changes made
>>>> >> > to the
>>>> >> > > >> > * packet (e.g. changes to VLAN) by secondary actions persist when
>>>> >> > those
>>>> >> > > >> > * actions are executed, although the original in_port is restored.
>>>> >> > > >> > *
>>>> >> > > >> > * Resubmit actions may be used any number of times within a set of
>>>> >> > actions.
>>>> >> > > >> > *
>>>> >> > > >> > * Resubmit actions may nest to an implementation-defined depth.
>>>> >> > Beyond this
>>>> >> > > >> > * implementation-defined depth, further resubmit actions are
>>>> >> > simply ignored.
>>>> >> > > >> > *
>>>> >> > > >> > * NXAST_RESUBMIT ignores 'table' and 'pad'. NXAST_RESUBMIT_TABLE
>>>> >> > requires
>>>> >> > > >> > * 'pad' to be all-bits-zero.
>>>> >> > > >> > *
>>>> >> > > >> > * Open vSwitch 1.0.1 and earlier did not support recursion. Open
>>>> >> > vSwitch
>>>> >> > > >> > * before 1.2.90 did not support NXAST_RESUBMIT_TABLE.
>>>> >> > > >> > */
>>>> >> > > >> > struct nx_action_resubmit {
>>>> >> > > >> > ovs_be16 type; /* OFPAT_VENDOR. */
>>>> >> > > >> > ovs_be16 len; /* Length is 16. */
>>>> >> > > >> > ovs_be32 vendor; /* NX_VENDOR_ID. */
>>>> >> > > >> > ovs_be16 subtype; /* NXAST_RESUBMIT. */
>>>> >> > > >> > ovs_be16 in_port; /* New in_port for checking flow
>>>> >> > table. */
>>>> >> > > >> > uint8_t table; /* NXAST_RESUBMIT_TABLE: table
>>>> >> > to use. */
>>>> >> > > >> > uint8_t pad[3];
>>>> >> > > >> > };
>>>> >> > > >> > OFP_ASSERT(sizeof(struct nx_action_resubmit) == 16);
>>>> >> > > >> >
>>>> >> > > >> > and in ovs-ofctl(8):
>>>> >> > > >> >
>>>> >> > > >> > resubmit:port
>>>> >> > > >> > resubmit([port],[table])
>>>> >> > > >> > Re-searches this OpenFlow flow table (or the
>>>> >> > table whose
>>>> >> > > >> > number is specified by table) with the
>>>> >> > in_port field
>>>> >> > > >> > replaced by port (if port is specified) and
>>>> >> > executes the
>>>> >> > > >> > actions found, if any, in addition to any
>>>> >> > other actions
>>>> >> > > >> > in this flow entry.
>>>> >> > > >> >
>>>> >> > > >> > Recursive resubmit actions are obeyed up to an
>>>> >> > implemen‐
>>>> >> > > >> > tation-defined maximum depth. Open vSwitch
>>>> >> > 1.0.1 and
>>>> >> > > >> > earlier did not support recursion; Open
>>>> >> > vSwitch before
>>>> >> > > >> > 1.2.90 did not support table.
>>>> >> > > >> >
>>>> >> > > >> >
>>>> >> > > >> > On Thu, May 03, 2012 at 09:54:08AM +0800, YIMIN CHEN wrote:
>>>> >> > > >> >> Hi Ben,
>>>> >> > > >> >>
>>>> >> > > >> >> Thank you for your reply! I saw there is some code about resubmit
>>>> >> > > >> >> Nicira extension action, but that seems to be in userspace
>>>> >> > ofproto.c,
>>>> >> > > >> >> not in datapath, so I didn't know that is related. Could you help
>>>> >> > > >> >> clarify for me how does resubmit work?
>>>> >> > > >> >>
>>>> >> > > >> >>
>>>> >> > > >> >> Thanks!
>>>> >> > > >> >> Yimin
>>>> >> > > >> >>
>>>> >> > > >> >> On Wed, May 2, 2012 at 12:40 PM, Ben Pfaff <blp at nicira.com> wrote:
>>>> >> > > >> >> > On Wed, May 02, 2012 at 10:53:10AM +0800, YIMIN CHEN wrote:
>>>> >> > > >> >> >> I am looking at ovs dp code, and is looking at a correct way
>>>> >> > for a
>>>> >> > > >> >> >> flow to traverse the table twice. The goal is like this:
>>>> >> > > >> >> >>
>>>> >> > > >> >> >> flow lookup => tbl_lookup()
>>>> >> > > >> >> >> perform actions => execute_actions() which changes the packet
>>>> >> > > >> >> >> flow lookup using the new packet => tbl_lookup()
>>>> >> > > >> >> >> perform actions on the new packet => execute_actions.
>>>> >> > > >> >> >
>>>> >> > > >> >> > Do you want the "resubmit" Nicira extension action?
>>>> >> > _______________________________________________
>>>> >> > dev mailing list
>>>> >> > dev at openvswitch.org
>>>> >> > http://openvswitch.org/mailman/listinfo/dev
>>>> >> >
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